Digital computing systems



May 14, 1963 s. RUHMAN ETAL 3,090,035

DIGITAL COMPUTING SYSTEMS Filed Oct. 25, 1954 2 Sheets-Sheet 1 May 14, 1963 Filed Oct. 25, 1954 S. RUHMAN ETAL DIGITAL COMPUTING SYSTEMS 2 Sheets-Sheet 2 /A/ VEA/maf SM/L Puf/MAN EL MEA? 7 Jo//A/sonr ilnite This invention relates to computing systems, and particularly to computing or counting in binary code by progressively shifting digital information-representing currents along a series of magnetically controlled circuits.

The invention provides means for preventing, or nullifying the effect of, undesirable oscillations and reverse current ow tendencies inherent in binary computing systems utilizing magnetic cores of a composition providing a rectangular or near rectangular hysteresis curve characteristic serially linked by digit-transferring windings and also by actuating windings upon which digitshifting currents are impressed intermittently, such devices being commonly called shift registers.

Because of the intermittent nature of the energization of the magnetic cores, and the fact that the duration of read-in and read-out pulses, particularly in high speed registers, is an extremely small fraction of a millisecond, the transformation of an individual magnetic core from a condition of saturation in one direction to a condition of saturation in the opposite direction is correspondingly rapid. This rapidity of energy transfer creates a problem in the matter of ridding the current-carryinnr actuation circuit or circuits of residual charge each time current ilow is cut off by pulse cessation. Each cutoff operation gives rise to a tendency toward residual energy ow in both directions throughout the various interlinked subcircuits, particularly during the off periods between entry of successive ux-driving, or shift, pu ses into the actuating windings of the successive cores. These residual currents are particularly troublesome in the shift-producing, or actuating, circuit or circuits because in such locations they have the potentiality of reversing the digital representations previously stored or registered in individual cores along the multi-stage computing line constituting the shift register. The more dense the pattern being stored and registered, the higher the frequency of cycling, or the more numerous the computing stages entering into a single registering line, the greater becomes this tendency toward reversal of the magnetic condition characterizing individual cores. In fact, with registers incorporating cores of low coercive force materials, even moderate conditions as to density, number of stages, or cycling speed may be sufficient to cause a build-up of residual current discharge during off periods of the register to a value high enough to cause read-in of l values (flux saturation in a predetermined direction) into cores which had just previously lost their l flux state, and for this reason, from the standpoint of maintaining the accuracy of the computation, should remain in the O flux state. The present invention provides a `method and means to nullify the error-producing propensities of such residual energy, the method herein proposed being to inter-pose a barrier to the flow of such residual energy in such a direction as to interfere with the correctness of digital representations incorporated into the cores by the normal functioning of the core linx-directing (shift) circuit.

Other objects and characteristics of the invention will become apparent upon reference to the lfollowing description of the embodiments of the invention illustrated in the accompanying drawings wherein:

`FIG. l is a diagrammatic view of a system embodying the invention;

States arent ice FIG. 2 is an equivalent circuit diagram illustrating electrical fact-ors inherent in the system;

FIGS. 3, 4a and 4b are graphs showing examples of voltage patterns at` different points in the system with and without inclusion of the present invention; and

FIG. 5 shows a second embodiment of the invention.

Referring lirst to FIG. l, the magnetic cores 10, 11, 12, and 13 have input windings i4, output windings 15, and actuation (shift) windings 16 (a, b, c, and d, respectively), the latter being serially connected in the plate circuit *17 of a driver tube 1S whose grid 19` receives signal voltage pulses at a rate (for example, kc. per second) determined .by the rate of pulse input to the primary winding 2! of a transformer 21 Whose secondary circuit 27 is connected to a source 28 of negative potential for cutoff bias of grid 19, the said secondary circut 27 also including a current-limiting resistor 29 in series relation to the secondary winding of the transformer and an oscillation absorbing resistor 30 in shunt relation to the secondary winding of the transformer. An inductance unit L22 may be inserted between plate 223 of the tube 18 and the shift winding 16a of the core 10, and a source of positive potential (for example, 200 volts) is provided at the opposite terminal 39 of the circuit l7. A second source 28a of positive potential (for example, volts) supplies screen grid 19a, while the suppressor grid and cathode of tube 1S are connected to ground potential as shown at 28b.

Pulses representing the information to be registered in the computer are applied to the terminals 26 of the lirst input winding 14 in code pattern. For example, if the information is in binary digital code, there may be a pulse applied for each digital interval wherein a binary l is to be registered, while a pulse will be omitted during each digital interval wherein a binary 0 is to be registered, successive digital intervals being measured by the repetition rate of the actuating (shift) pulses applied to shift windings 16 (a to d) under the control of trans-former 21 and driver tube "18 during the on period of a length, as represented in FIG. 3, which is a graph of voltage development across the plate-cathode circuit of driver tube 18, during the successive stages of each digital interval, stage a being marked by a sharp voltage drop from the B+ level toward the zero point as the tube 18 begins to conduct, then a momentary rise as the tube tends to ickerf then a more or less steady lower level for the remainder of the shift pulse period a. When excitation of grid 19A ceases and the tube 18 stops conducting, there is a sudden rise of voltage as energy applied to circuit 17 is converted into storage charges tending to satisfy the distributed capacitance and inductance values C1 to C5 and L1 to L5, shown in FlG. 2 and more fully explained hereinafter. This capacitance charging occurs during portion b ('FIG. 3) of the cycle, and is followed by rapid discharge of the capacitance energy during stage c, and by a ringing tendency during stage d, the latter being due largely to inductance leakage from the cores 10 to I13:.

The presence of a pulse of positive polarity in winding le of the frrst magnetic core 10 will cause said core to become saturated in what may be regarded as the positive direction of flux ow; hence the next succeeding shift pulse applied to shift winding 16a of core 10 (assuming the polarity of all such shift pulses to be such as to produce a condition of negatively directed saturation in the core l0) will shift the magnetization of the core 10 to its opposite saturation state, whereupon there will be generated in the output Winding "15 of core 10 a high amplitude pulse whose charge will be delivered to the rst of a series of storage condensers 31, 32, 33, and 34. The charge thus delivered to condenser 311 will then begin to ilow toward the input Winding 14 of the next suc- -with normal kfunctioning of the register.

ceeding core 11, but the major portion of Vthe charge will yremain in the condenser I:i1 for the duration of the contemporaneous period of shift pulse application (measured in microseconds) the shift pulse occupying, however, only the minor portion a of the complete digital interval, as above noted. As the loaded condensers 31 to 34, that is, those condensers holding current charges representative of l values, discharge current into the input windings 14 of the adjacent cores to accomplish the read-in function above described, the rate of Such discharge is abruptly stepped up at the moment of conclusion of shift pulse application. Because of such sudden rise in the current discharge rate of these l carrying condensers there is a rapid magnetic flux reversal in those cores receiving these l read-in current surges, Such rapid flux reversal will cause current generation not only in the input windings 14 of such cores (to fuliill the l registering function) but will also operate to charge the distributed capacitance values inherent in the shift windings 16 of lthe same cores, as above noted. These capacitancevalues (indicated at C2 to C5 in the equivalent circuit shown in IFIG. 2), as well as the capacitance value (C1 of FG. 2) inherent in tube 18, will be absorbed by the line 17 during the continuation of the read-in process above `referred to. When this readin process (which occupies the b portion of the cycle, as shown in FIG. 3) is substantially completed, there will be a relatively rapid discharge by the capacitance units C1 to C5 of lthe current just previously absorbed therein as above described. This rapid current discharge from the capacitance units C1 to C5 will coincide with the c period (FIG. 3) of sharp voltage drop in line `17 from the maximum voltage point which occurred at the height of the'above-described read-in process. This capacitance current discharge will be supplemented by concurrent inductance leakage as represented by the inductance values L1 to L5 (FIG. 2) inherent in the constituent components of line 17 as indicated.

fhese discharging currents flowing in stages c and d (FIG. 3) of the olf period of the shift pulse will be lflowing in a direction opposite to the direction taken by the shift pulse current when the latter is on. This can be explained .as follows:

There is a pre-established relationship between each shift coil 16 (a to d) and its associated magnetic core such that normal `current passing through the shift coil will be in the -direction to read a value into the associated core; hence any 0 value-establishing flux -change in the core will necessarily induce a correspondingly directed current charge into the shift coil. In other words, capacitance charging of a shift coil and normal feeding of shift pulses to such shift coil will occur in one and the same direction and, conversely, capacitance discharging from a shift coil will tend to occur in the opposite direction. This latter direction, that is, the direction of iiow of the capacitance discharging current, is opposite to the working or effect-ive direction of liow established by the B+ potential for the actuating circuit 17; and as this ldischarge current is subjected to its greatest reverse voltage motivation during the c (FIG. 3) portion of the o period, when pulse energy application to the shift windings 16 is undesirable, it interferes In fact, with hi-gh frequency of pulse application or with high density in the informational pattern lbeing transmitted, as above noted, these discharge currents may actually cause l values to be registered spuriously, thus introducing erroneous computations.

It has been found that the above-described diiiiculty can be corrected by interposing, at one or more selected locations along the line of the shift circuit 17, current flow-interrupting means capable of preventing any ef- -fective application of reverse actuating voltage to the individual shift windings 16 for the duration of the olf periods during which tube 1S is not conducting. As ilpspectively, of FIG. 1.

lustrated in FIGS. l and 2, such preventive means takes the form of uni-directionalfimpedance elements, such as the crystal diodes 40 to 44, inclusive, illustrated as located in the several sections into which line 17 may be regarded as being divided by the successive shift windings 16, these diodes being so poled as to permit free passage of current from the source 39 of positive potential during any period when tube 18 is conducting, while on the other hand operating to open-circuit, and thus cie-energize, all shift windings 16 (a to d) during every period when tube 18 is not conducting. The use of such diodes in these several sections of line 17 operates to convert the sharp voltage drop at c (FIG. 3) into a much more gradual and attenuated recession (as indicated by the dash-line valternate curve section e in FIG. 3) by providing almost complete elimination of current ilow in the olf periods of driver 18. Substantial correction of the reverse current effects may be obtained Aby use of the single diode 44, adjacent terminal 39; hence the other diodes lill, 411, 42, and 43 may be omitted except lwhere extreme sensitivity characterizes the installation and thus calls for maximum protection atall key points.

FIGS. 4a and 4b are voltage patterns of the read-in voltage across any one of the condensers 31 to 34 as it develops from cycle to cycle during circulation of a binary pattern of digital values along the successive stages of a register, such as that illustrated in FIG. 1, except that the particular register that would be employed to obtain the voltage patterns illustrated in FIGS. 4a and 4b would be a seven-stage register. The digital pattern applied to the register, as shown, is a pattern of six l values followed by a single 0 value. FIG. 4a shows the G voltage reading as building up to a value approaching that of the l readings, hence coming objectionably close to the point where it might cause a spurious l value to be entered in the register. This is a condition frequently occurring in the absence of the protecting diodes 41 to 44 provided by the present invention. FIG. 4b, on the other hand, shows how the diodes 41 to 44 (or even the single diode 44) holds the 0 voltage development to a safe low value relative to the much higher 1 values, it being possible to maintain a ratio of at least S-to-l 4between the "1 and 0 voltage readings `by the inclusion of the diode control factor.

HG. 5 shows the invention applied to a magnetic core register having dual shift lines 4with sequential application of shift pulses thereto. In this FIG. 5 arrangement the magnetic cores 10a, 11a, 12a and 13a correspond to the cores 10, 11, 12, and 13, respectively, of FIG. l, and the cores 31a, 32a, 33a, and 34a correspond (functionally) to the condensers 31, 32, 33, and 34, re-

Also input, output, and shift windings 14a, 15a, and 46a (or 4619 as the case may be) correspond to windings 14, 15, and 16, respectively, of FIG. l.

With this FIG. S arrangement, one cycle of operation consists of, lirst, applying a shift pulse to the principal Vcores 10a, 11a, `12a and 13a, and secondly, to the auX- iliary cores 31a, 32a, 33a, and 34a. If a l value is stored in core lila, the application of a shift pulse thereto (by way of shift line 17a and windings 46a) will cause transfer of the i value to auxiliary core 31a. Then, as a shift pulse is applied to line 17b and windings 4611, the l value will move along from core 31a to principal core 11a, to complete the digit-transferring cycle. These lines 17a and 176 will be subject to the same reverse current flow tendencies as line 17 of FIG. 1, due to the alternating conditions of conduction and non-conduction through driving tubes `13a and 1817, respectively, and the` effect thereof in producing alternate charging and discharging of the distributed capacitance of lines 17a and 17b in a manner corresponding to the action occurring in line 17 of FIG. l, as above explained. The prevention of such reverse iiow can be accomplished in analogous fashion, namely, by inserting diodes 44a and 44h in the lines 17a and 17b, respectively, as indicated in FIG. 5, thereby preventing current iiow toward source 39 during the ofi periods of tubes 18a and 18b, respectively.

The diodes 36 and resistors 37 of FIGS. l and 5 function as current direction and oscillation controls, respectively, and in serving these purposes they behave as more `fully described in copending patent application No. 395,- 692, filed December 2, 1953, and assigned to the assignee of the subject invention, their counterparts being the diodes and resistors 34 of said copending application.

Alternatively, diodes 41 to 44 of FIG. l (or diodes 44a and 44h of FIG. 5) may be replaced by electronic switching means interrelated with tube 18 (or with tubes .18a and `18h as the case may be) in such manner as to establish an open circuit in line 17 (or lines 17a and 17b) for the duration of each 0H period of tube 18 (or tubes 18a and 18h). Again, the desired result may be achieved by adding a controlled path for draining ofI' to ground or to other suitable potential levels, all undesirable current owing in line 17 (or lines 17a and 17h) during such o periods.

Many other modifications will be apparent to persons skilled in the ar-t, and it is accordingly desired that this invention be not limited to the particular details of the embodiments illustrated herein, except to the extent defined by the appended claims.

What is claimed is:

l. In a magnetic control system comprising a plurality of magnetic cores and windings interlinking said cores for the transfer of electrical current along conductors interconnecting said windings, means including an actuating circuit including an actuating Winding interlinking each of said cores `for generating currents in those windings associated with magnetic cores possessing a predetermined direction and magnitude of uX content, means including an electronic device having alternate on and off periods for controll-ing generation of such currents periodically, means inherent in the capacitance aspects of said system for establishing a tendency toward current liow in said actuating circuit during ofi periods in a direction opposite to the direction of flow prevailing during said on periods, and a rectier incorporated into said actuating circuit adjacent to each actuating winding to nullify said tendency due to said capacitance.

2. In a magnetic control system comprising a plurality of magnetic cores and a corresponding plurality of coils wound about said cores, shift-producing means including additional windings on each of said cores for controlling generation of current in said rst-named coils, said means having inherent therein capacitance to cause unwanted current flow in said last-named windings between the intervals of controlled current generation in said first-named coils, and a rectilier having direct electrical connection with each of said last-named winding for nullifying said unwanted current flow between said intervals.

3. A single core-per-bit magnetic control system comprising a plurality of magnetic cores, input and output circuits interlinking said cores, a third circuit including an actuating winding on each of said cores controlling the operation of said input and output circuits, means for energizing said third circuit at predetermined time intervals, means for producing delayed current flow in said input circuits and thereby inducing voltage into said third circuit, and a plurality of rectifiers forming a part of said third circuit for preventing flow of reverse current in each actuating winding in said third circuit when voltage is induced therein during operation of said delayed current iiowproducing means.

4. A magnetic control system comprising a plurality of magnetic cores, input and output circuits interlinking said cores, a single third series-connected core circuit comprising a separate actuating Winding on each magnetic core controlling the operation of said input and output circuits, means for supplying current in one direction to said third circuit at predetermined time intervals, means `for producing delayed current flow in said input circuits and thereby inducing voltage into said third circuit in a direction opposite to the voltage gradient prevailing in said third circuit during said predetermined time intervals, and a rectifier `connected in series with each actuating winding rendering said oppositely directed voltage inefective to produce current iiow.

5. A magnetic control system comprising a magnetic core having input and output windings applied thereto, an actuating circuit including series-connected actuating windings controlling the operation of said input and output windings, means for supplying current in one direction to said actuating circuit at predetermined time intervals, ternporary storage means for producing delayed current flow in said input winding and thereby inducing unwanted residual voltage into said actuating circuit during time periods alternating with said predetermined time intervals, and a rectifier connected in series with each actuating winding permitting current flow only in one direction for rendering said residual induced voltage ineffective.

6. In a magnetic control system, a magnetic core having an input winding, means including an actuating circuit having an actuating winding on each core and a current storage circuit for producing delayed current ow in said input winding, a source of energy for said actuating circuit, means for cutting ot said source of energy during the period of delayed current flow in said input winding, and a rectifier connected in series with each of said actuating windings for rendering ineiective any voltage induced into said actuating circuit, by way of said magnetic core, during said cut-off period.

References Cited in the file of this patent UNITED STATES PATENTS 2,652,501 Wilson Sept. l5, 1953 2,654,080 Browne Sept. 29, 1953 2,680,819 Booth June 8, 1954 2,697,178 Isborn Dec. 14, 1954 2,719,961 Karnaugh Oct. 4, 1955 2,751,546 Dimmer ,June 19, 1956 

1. IN A MAGNETIC CONTROL SYSTEM COMPRISING A PLURALITY OF MAGNETIC CORES AND WINDINGS INTERLINKING SAID CORES FOR THE TRANSFER OF ELECTRICAL CURRENT ALONG CONDUCTORS INTERCONNECTING SAID WINDINGS, MEANS INCLUDING AN ACTUATING CIRCUIT INCLUDING AN ACTUATING WINDING INTERLINKING EACH OF SAID CORES FOR GENERATING CURRENTS IN THOSE WINDINGS ASSOCIATED WITH MAGNETIC CORES POSSESSING A PREDETERMINED DIRECTION AND MAGNITUDE OF FLUX CONTENT, MEANS INCLUDING AN ELECTRONIC DEVICE HAVING ALTERNATE "ON" AND "OFF" PERIODS FOR CONTROLLING GENERATION OF SUCH CURRENTS PERIODICALLY, MEANS INHERENT IN THE CAPACITANCE ASPECTS OF SAID SYSTEM FOR ESTABLISHING A TENDENCY TOWARD CURRENT FLOW IN SAID ACTUATING CIRCUIT DURING "OFF" PERIODS IN A DIRECTION OPPOSITE TO THE DIRECTION OF FLOW PREVAILING DURING SAID "ON" PERIODS, AND A RECTIFIER INCORPORATED INTO SAID ACTUATING CIRCUIT ADJACENT TO EACH ACTUATING WINDING TO NULLIFY SAID TENDENCY DUE TO SAID CAPACITANCE. 